Need recommendations for high gain/small footprint class d amplifier

I think your best choice so far (if you can or are willing to afford it) would be the Benchmark AHB2, which has dimensions of 11.04" W x 3.47" H x 8.33" D and a gain ratio close to what you’ve been considering.

29.3dB (8 ohm) -> 29.1dB (3 ohm) -> 28.07 (2 ohm) (note: converted from voltage gain Benchmark has published)

More importantly, in my opinion, is the amplifier’s efficiency as I advocate earlier (see below). This is the best specification I have seen from a reasonably priced ($3,500) yet highly respected amplifier. The only amplifier I’ve come across with up to 100% efficiency at a 2-ohm load is Accuphase class A series such as A80, which could cost you more than $10k. Almost all Hypex- or Purifi-based class D amplifiers fall short in this regard at 2 ohm load impedances.

• 100 Watts per channel into 8 Ohms, both channels driven
• 130 Watts per channel into 6 Ohms, both channels driven (97.5%)
• 190 Watts per channel into 4 Ohms, both channels driven (95%)
• 240 Watts per channel into 3 Ohms, both channels driven (90%)
• 259 Watts per channel into 2 Ohms, both channels driven (64.8%)

@lcherepkai in my custom speakers, which I was told should be about a 3 ohm load.

It seems like you never measure your custom speakers. Try using REW to measure the impedance-phase angle versus frequency yourself, and then compute the EPDR using a more refined empirical equation (from Stereophile) that I derived in my post in the following thread. EPDR will reveal the most critical load impedance you are likely to encounter. For nominally 3-ohm-rated speakers, depending on the phase angle, you will likely face impedances below 2 ohms in the mid- or upper-bass frequency range. This is why I strongly urge you to carefully consider the amplification efficiency of the power amplifier when dealing with speakers rated for a 2-ohm load.

https://forum.audiogon.com/discussions/impedance-the-most-ignored-and-useful-measurement-tool

My Buchardt S400 MKII is rated at 4 ohms, but the EPDR drops as low as 1.5 ohms at 110Hz—very demanding. Even my Parasound 125-150 watt high-current power amplifier (35-45 amps peak) could not drive it efficiently. I need to place the speaker closer to the front wall to achieve better bass response, but this comes at the cost of compromising soundstage depth. Check out the impedance-phase angle and EPDR vs. frequency chart posted for S400 II by Erin, and you’ll see what I’m talking about.

lanx0003---only their NC2K monoblocks have sufficient gain, 31dB, all their other amps are 25db at the high setting, but you do make a good point to consider.  I guess the best thing to do is just go to all the class d amp manufacturers websites and compare directly.  That'll be time consuming, and I was just hoping for some recommendations that actually are in 30+dB range.  Thanks

Burson.

If you decide to go with Hypex NCORE like Buckeye, spend a little ($300) more to get NCOREx line such as NCx500 instead of NC502MP. The amplification efficiency (A.E.) is better for handling lower impedance loads

https://www.buckeyeamp.com/shop/amplifiers/hypex/ncx500/2_channel

Speaker Imp. NC502MP  A.E.    NCx500    A.E.

2 ohm            450 watts  32%    700 watts  46%

4 ohm            500 watts  71%    700 watts  92%

8 ohm            350 watts    -        380 watts    -

Price                 $695                     $995

As shown, NCx500 will handle 4 ohm load speaker much better.  The amp efficiency from both models for 2 ohm load are still not great but not bad for handling not so demanding low imp. speakers for the price.

Thanks mapman.  I'll look further into Class D Audio.  I'm not thrilled with that industrial look you mentioned but the size and sound are the major factors for me... well, and price of course.  

@icherepkai you certainly could use them just for low end but they are designed for and most capable full range.

I like the casing designed for ventilation and the somewhat industrial look actually. Very unique. Also when you turn it on you get some cool flashing led effects from within as it powers up. The dimly lit power button is a nice touch. It’s about half the size or less of the Schitt Freya pre-amp I use it with.

higher gain than the Red Dragon S-500

Why???? This is a typical problem for any active crossover and we solve this with attenuation of the gain.  QED.

Hello Erik.   The bass amp needs to be higher gain than the Red Dragon S-500 I'm using to drive the satellite section of my large Legacy Focus clone/diy speakers.  These use Eton drivers, 2 midbass, midrange, tweeter per side, and these drivers are significantly more efficient than the woofers.  When I first acquired these speakers, I bi-wired but did not bi-amp them and I was shocked out just how little bass I was getting despite 4 12" woofers.  Eventually, I did bi-amp, using a pro amp with the volume control pots to gain-match to a large SET in the colder months and a gainclone in the warmer ones, via the RCA outputs.  My source was a Raysonic 228 cdp which I ran directly into both amps simultaneously.  The player was tubed and the RCA outputs were connected to the valves while the XLR outputs were solid state, exactly what you'd want connected to the bass amp.  

   I'm now using either a Bel Canto DAC 2.8 or Audio Alchemy DDP-1 and the balanced outputs are the ones I use to drive the Red Dragon powering the satellite section of the speakers.  I have to run the bass amp from the RCA outputs which are half the gain of the XLR outputs, so it becomes necessary to have a higher gain amp on the woofers.  I use an NHT X-2 active crossover only on the bass drivers and it allows for +10dB of gain, which full up with the D-sonic amp (rated gain of 26dB), is just adequate on most material/recordings, but can be insufficient on other material where extra bass would be desirable.  I did insert an active preamp, a Kingrex PREference, between the crossover and the bass amp briefly.  It gave me plenty of additional gain but lost a bit of detail and could easily get boomy.  

    With the Jaton amp as the bass amp, with a gain of 32dB, I seldom turn the NHT X-2 up all the way so, it's obvious to me, going with a higher gain amp is the way to go.  I'm just looking for a decent but affordable class d amp with sufficient power and that higher gain to take over the bass duty.  I know the mentioned Channel Islands D-500 monoblocks fit the bill but really don't want to spend quite that much and then I'll need to get another matching power cord for the other bass amp.  

   So, I think you'll be able to see the importance of a higher gain amp in my application and yes, there are low-gain class d amps.  I've seen a few listed at or below 20 dB, which would be useless as the bass amp in my system.  

I'm using classdaudio on my tweeters on the infinity irs v and they sound good. I also have some d sonic and have no  trouble matching gain with other pre amps.enjoy the search.

Um, kind of curious why "high gain" suddenly came into the picture.  Most amplifiers are between 20 and 30 dB I believe.  Are there "low gain" class D?

mapman:  would you use the Ganfet amp(s) solely to power woofers?  What I've read about them is quite positive but, I'm not a fan of their appearance.  I like their older cases much better.  

The Class D Audio Ganfet amps are small yet  awesome  and have a jumper on the back for low medium or high gain.  I use medium setting to get to decent SPL with a Schitt Freya pre-amp set on low gain output.  

The CLass D Audio amps can have a gain over 30dB but the Buckeye and the Bel Cantos are 26 and 27 respectively.  In my system, the woofers are significantly lower in sensitivity than the rest of the drivers so, to compensate, I do need an amp with higher gain.  I'm temporarily using a Jaton AV 5140, which only puts out 140w into a 4 ohm load, but has a gain of 32dB.  This allows me to get the same output level from the woofers as the satellite section of my speakers but a lower gain amp, even with crossover set at +10dB sounds a bit thin and lightweight.  I have a D-Sonic amp and the gain is specified at 26db, with the output level on the crossover full up, the bass output is still lower than the rest of the speaker so.... really need something with a gain of over 30dB and the power to back it up.  Thanks for the options and please keep them coming.  

I hold Bel Canto amps in high regard.  Here’s one that might fit the bill…

https://www.ebay.com/itm/135585206696

Best of luck. 

https://www.buckeyeamp.com/shop/amplifiers/hypex/nc502mp/2_channel

Small form factor, high power.  Using with KEF LS50 speakers.  Sounds great.

@lcherepkai  ihttps://classdaudio.com/